1. Cross-Reference to Related Applications
Not Applicable.
2. Field of the Invention
The present invention relates generally to pivot bearing cartridges use in a head stack assemblies, and more particularly to a pivot bearing cartridge having inner and outer ball bearing sets.
3. Description of the Prior Art
The typical hard disk drive includes a disk drive base, and a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to the disk drive base. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA) that includes at least one transducer head, typically several, for reading and writing data from the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The heads stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional xe2x80x9crotaryxe2x80x9d or xe2x80x9cswing-typexe2x80x9d actuator assembly typically comprises an actuator body that rotates on a pivot assembly between limited positions, a coil portion that extends from one side of the actuator body to interact with one or more permanent magnets to form a voice coil motor, and one or more actuator arms which that extend from an opposite side of the actuator body. A head gimbal assembly includes at least one transducer head, sometimes two, which is distally attached to each of the actuator arms. The actuator assembly includes the actuator body which has a bore and a pivot bearing cartridge engaged within the bore. The at least one head gimbal assembly and the flex circuit cable assembly are attached to the actuator assembly.
The pivot bearing cartridge typically includes a pivot shaft having a threaded end, a pivot sleeve, and vertically separated upper and lower ball bearing sets mounted upon the pivot shaft which facilitate rotational attachment of the pivot sleeve to the pivot shaft. The pivot sleeve is disposed within the bore of the actuator body for allowing the pivoting of the actuator assembly. The threaded end of the pivot shaft used to mount the pivot bearing cartridge, and therefore the actuator assembly, to the disk drive base. Each ball bearing set includes inner and outer ball bearing races which encase a plurality of ball bearings. The inner ball bearing races engage the pivot shaft and the outer ball bearing races engage the pivot sleeve. This configuration allows for rotational movement of the outer ball bearing races relative to the inner ball bearing races for rotation of the pivot sleeve. The upper and lower ball bearing sets are pre-loaded in compression to maintain the pivot sleeve in position with respect to the pivot shaft.
A topic of concern is the desire to reduce the overall disk drive size. Such disk drives may have a variety of applications such as in hand held or portable electronic devices. The exterior size and shape of the disk drive is often referred to as a xe2x80x9cform factorxe2x80x9d. Reduction of such disk drive form factor has proven challenging. This is because the mere reduction of the size of the various disk drive components may result in such components being unable to conform to required specifications and standard form factors for such components, and may result in installation or assembly difficulties. As such reduced sized disk drives may have applications in hand held or mobile electronic device, the specifications may be even be tighter as compared to personal computer applications. For example, those specifications related to susceptibility to damage resulting from shock.
One particular area of focus is the reduction of the height of the pivot bearing cartridge as this limited the over all sizing of the head stack assembly. In a typical configuration, the pivot bearing cartridge height may be a function of the upper and lower ball bearing set arrangement. The mere reduction of the sizing of the upper and lower ball bearing sets impacts the susceptibility to damage resulting from shock, potential use of non-standard form factor bearings and difficulties conforming to allotted space requirements for such bearings. Accordingly, there is a need in the art for an improved pivot bearing cartridge configuration in comparison to the prior art.
An aspect of the invention can be regarded as a pivot bearing cartridge for use in a head stack assembly. The pivot bearing cartridge is provided with a pivot bearing cartridge base. The pivot bearing cartridge is provided with a pivot shaft in mechanical communication with the pivot bearing cartridge base. The pivot bearing cartridge is provided with an inner ball bearing set surrounding the pivot shaft. The inner ball bearing set has a first inner race and a first outer race. The first inner race is attached to the pivot shaft. The pivot bearing cartridge is provided with an outer ball bearing set surrounding the inner ball bearing set. The outer ball bearing set has a second inner race and a second outer race. The second inner race is fixed relative to the first outer race.
Preferably, the inner and outer ball bearing sets are pre-loaded in compression. The first inner race may be axially off-set from the first outer race, and the second inner race may be axially off-set from the second outer race. The second inner race may be attached to the first outer race. Further, the outer ball bearing set may have a cross sectional size different than a cross sectional size of the inner ball bear set.
In an embodiment of the present invention, the pivot bearing cartridge is further provided with a pivot bearing cartridge cap. The motor shaft is attached to the pivot bearing cartridge cap. Thus, in this embodiment, the pivot shaft is rotatable. The pivot bearing cartridge cap has a cap annular member extending from the pivot bearing cartridge cap, and the cap annular member is attached to the second outer race. The pivot bearing cartridge base has a base annular member extending from the pivot cartridge base, and the base annular member is attached to the first outer race and the second inner race.
In another embodiment of the present invention, pivot shaft is attached to the pivot bearing cartridge base. Thus, in this embodiment, the pivot shaft is stationary. The pivot bearing cartridge base has a base annular member extending from the pivot cartridge base, and the base annular member is attached to the second outer race. The pivot bearing cartridge is further provided with a pivot bearing cartridge cap, and the cap annular member is attached to the first outer race and the second inner race.
In addition, according to another aspect of the present invention, there is provided a head stack assembly that includes an actuator body and a pivot bearing cartridge according to an above described embodiment. The actuator body is provided with a bore and the pivot bearing cartridge is disposed within the bore. As the pivot bearing cartridge may be provided with a pivot bearing cartridge cap, the pivot bearing cartridge cap may be utilized as a pivot sleeve for engaging the bore.